@inproceedings{FialaRabensteinMaschwitz1994,
  author    = {Fiala, Brigitte and Rabenstein, R. and Maschwitz, Ulrich},
  title     = {Ant-attracting plant-structures: Food bodies of SE Asian Vitaceae},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-55177},
  year      = {1994},
  abstract  = {No abstract available},
  subject      = {Pflanzen},
  language  = {en}
}
@phdthesis{Eckert2000,
  author    = {Eckert, Martin},
  title     = {Zur Regulation und Expression von Aquaporinen unter Ber{\"u}cksichtigung des pflanzlichen Wasserhaushaltes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-1114},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2000},
  abstract  = {Die Methodik und Technik der Gaswechselmessung von Pflanzen wurde f{\"u}r den Modellorganismus Arabidopsis thaliana optimiert und f{\"u}r Untersuchungen zur Beteiligung des Aquaporins PIP1b an Wassertransportvorg{\"a}ngen w{\"a}hrend der Stoma{\"o}ffnung verwendet. Die Messungen der Transpirationsraten von PIP1b-Antisense-Pflanzen ergaben keine Hinweise auf Ver{\"a}nderungen des zeitlichen Verlaufs der Stoma{\"o}ffnung. Die Wasserpermeabilit{\"a}ten von Schließzell-Plasmamembranen scheinen somit nicht von der Expression des Aquaporins PIP1b beeinflußt zu sein. - Gaswechselmessungen an Nicotiana tabacum NtAQP1-Antisense-Pflanzen zeigten eine Verringerung der Transpirationsraten im Licht und eine geringere Grundtranspiration im Dunkeln. Dies deutet auf eine Beteiligung von NtAQP1 am Wassertransport hin. - Ausgew{\"a}hlte Arabidopsis thaliana-Mutanten wurden hinsichtlich ihrer stomat{\"a}ren Antwort auf Rot- und Rot-/Blaulicht-Bestrahlung analysiert. Hierf{\"u}r wurde ein Doppelbestrahlungs-Protokoll entwickelt. Vergleiche mit den Wildtypen ergaben signifikante Unterschiede bei der Phytochrom-Mutante phyA-103, der Abscisins{\"a}ure-Mutante aba3-2 und der Auxin-resistenten Mutante axr1-3. Ferner zeigte die Mutante npq1-2 nicht die beschriebene Abweichung der stomat{\"a}ren Antwort auf Blaulicht. - Die Expressionsmuster eines PIP1b-GFP-Reportergens in transgenen Arabidopsis thaliana-Pflanzen wurden analysiert. Hohe Promotor-Aktivit{\"a}ten konnten in meristematischen Bereichen von Wurzel und Sproß, in Elementen der Leitb{\"u}ndel, in jungen Kotyledonen und in Staubbl{\"a}ttern beobachtet werden. Es zeigte sich eine enge Korrelation zwischen PIP1b-Promotoraktivit{\"a}t und Streckungswachstum. - Eine Sequenzanalyse des NtAQP1-Promotors ergab {\"U}bereinstimmungen mit spezifischen Bindungsmotiven von MYB-{\"a}hnlichen Transkriptionsfaktoren. Mit Promotor-Reportergenen konnte die Beteiligung eines dieser Sequenzmotive an der GA- und ABA-induzierten Aktivierung des NtAQP1-Promotors gezeigt werden. Zur Analyse der Phytohormon-Wirkungen auf deletierte Promotorbereiche wurde ein duales Vektorsystem entwickelt und bei der transienten Transformation von BY2-Protoplasten eingesetzt. - Die Expression eines GFP::NtAQP1-Fusionsgens in BY2-Zellen zeigte die subzellul{\"a}re Lokalisation des Aquaporins in der Zytoplasmamembran. Ferner wurde Fusionsprotein in Vesikel-{\"a}hnlichen Strukturen beobachtet.},
  subject      = {Pflanzen},
  language  = {de}
}
@phdthesis{Imbusch2001,
  author    = {Imbusch, Ruth},
  title     = {Phytoprostane F1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-1182238},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2001},
  abstract  = {Isoprostane F2 sind Autoxidationsprodukte der Arachidons{\"a}ure, die {\"u}ber radikal-katalysierte Oxidation entstehen. Bei einigen Erkrankungen im Tier konnte gezeigt werden, daß die Konzentration von Isoprostanen F2 mit dem verst{\"a}rkten Vorkommen von freien Radikalen korreliert, weshalb Isoprostane heute als Marker des oxidativen Streß genutzt werden. Dar{\"u}ber hinaus weisen einige Isoprostane eine biologische Aktivit{\"a}t auf, weshalb sie heute als Signalstoffe des oxidativen Streß im Tier diskutiert werden. Pflanzen hingegen k{\"o}nnen keine Isoprostane F2 synthetisieren, da ihnen der Precursor Arachidons{\"a}ure fehlt. In der vorliegenden Arbeit wird gezeigt, daß analog zu den Isoprostanen F2 Phytoprostane F1 in Pflanzen aus Linolens{\"a}ure gebildet werden. Hierf{\"u}r wurden HPLC- und Gaschromatographie-Massenspektroskopie-Methoden entwickelt, die eine Quantifizierung von Phytoprostanen F1 in Pflanzen erm{\"o}glichten. In frischen Pflanzenorganen wurden Phytoprostane F1 sowohl in freier als auch in veresterter Form detektiert. Dar{\"u}ber hinaus stieg die Konzentration sowohl freier als auch veresterter Phytoprostane F1 in Pfefferminzbl{\"a}ttern nach Verwundung und in pflanzlichen Zellkulturen nach Zusatz von Agentien, von denen bekannt ist, daß sie pflanzliche Zellen oxidativ sch{\"a}digen, an. In getrockneten Pflanzenmaterialien wurden extrem hohe Konzentrationen an Phytoprostanen F1 quantifiziert. Daher steht die Vermutung nahe, daß Phytoprostane F1 {\"a}hnlich wie die Isoprostane F2 im Tier als sensitiver Marker der oxidativen Zellverletzung in der Pflanze eingesetzt werden k{\"o}nnen. Dar{\"u}ber hinaus konnte gezeigt werden, daß der Zusatz von Phytoprostanen F1 zu Eschscholzia californica-, Crotalaria cobalticola- and Thalictrum tuberosum-Zellsuspensionskulturen zu einer Phytoalexinakkumulation f{\"u}hrte.},
  subject      = {Pflanzen},
  language  = {de}
}
@phdthesis{Roesch2002,
  author    = {R{\"o}sch, Petra},
  title     = {Raman-spektroskopische Untersuchungen an Pflanzen und Mikroorganismen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-3539},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2002},
  abstract  = {In dieser Arbeit werden Pflanzen, Pflanzengewebe, Pflanzenzellen und Mikro-organismen spektroskopisch untersucht und ihre Inhaltsstoffe unter minimaler Probenpr{\"a}paration im biologischen Gewebe direkt lokalisiert und identifiziert. Unter den verf{\"u}gbaren Schwingungs-spektroskopischen Methoden ist die Mikro-Raman-Spektroskopie f{\"u}r diese Fragestellungen besonders gut geeignet, da Wasser Raman-Spektren nur wenig beeinflusst. Daher kann mit Raman-spektroskopischen Methoden auch in stark wasserhaltigem Gewebe gemessen werden. Weiterhin erh{\"a}lt man mit der Mikro-Raman-Spektroskopie eine gute r{\"a}umliche Aufl{\"o}sung im sub-µm-Bereich, wodurch es m{\"o}glich ist, heterogene Proben zu untersuchen. Dar{\"u}ber hinaus kann die Mikro-Raman-Spektroskopie mit anderen Methoden, wie z. B. der oberfl{\"a}chenverst{\"a}rkten Raman-Spektroskopie (SERS), kombiniert werden. In pflanzlichen Zellen liegt eine Vielzahl von Substanzen in geringen Konzentrationen vor. Aufgrund der niedrigen Quantenausbeute des Raman-Effekts treten vor allem Substanzen, die eine Resonanz-Verst{\"a}rkung erfahren, in den Spektren hervor. Diese Substanzen, wie z. B. b-Carotin, k{\"o}nnen deshalb in geringen Konzentrationen detektiert werden. Der Schwerpunkt dieser Arbeit liegt in der Untersuchung von Sekund{\"a}r-Metaboliten wie Alkaloiden, Lipiden oder Terpenen, die in der Pflanze agglomerieren. Neben der Identifikation von Inhaltsstoffen, k{\"o}nnen die Raman-Spektren von Pflanzen f{\"u}r die chemotaxonomische Klassifizierung mit Hilfe der hierarchischen Clusteranalyse verwendet werden. Die Identifizierung von Mikroorganismen auch in sehr geringen Mengen (Monolage, einzelne Zellen) ist mit der Mikro-Raman-Spektroskopie nur unter bestimmten Voraussetzungen durchf{\"u}hrbar. F{\"u}r weitergehende Untersuchungen wird hier die SERS-Sonde oder ein TERS-Aufbau verwendet werden.},
  subject      = {Pflanzen},
  language  = {de}
}
@phdthesis{Thoma2003,
  author    = {Thoma, Ingeborg},
  title     = {Cyclopentenon-Phytoprostane als Induktoren von pflanzlichen Abwehrreaktionen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-6857},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2003},
  abstract  = {Lipidperoxidation kann entweder durch Lipoxygenasen oder reaktive Sauerstoffspezies ausgel{\"o}st werden. Enzymatische Oxidation von alpha-Linolens{\"a}ure kann zur Biosynthese von zyklischen Oxylipinen vom Typ der Jasmonate f{\"u}hren, wohingegen durch freie Radikal-katalysierte Oxidation von alpha-Linolens{\"a}ure mehrerere Klassen zyklischer Oxylipine, den Phytoprostanen entstehen k{\"o}nnen. Eine dieser Phytoprostanklassen, Phytoprostane E1 (PPE1), kommen ubiquit{\"a}r in Pflanzen vor. In der vorliegenden Arbeit wird gezeigt, dass PPE1 in planta in neuartige Cyclopentenon-Phytoprostane, die PPA1 und PPB1 umgewandelt werden. Eine gesteigerte Bildung von PPE1, PPA1 und PPB1 wurde sowohl nach Peroxid-Behandlung von Tabak-Zellkulturen als auch nach Behandlung von Tomatenpflanzen mit dem nekrotrophen Pilz Botrytis cinerea beobachtet. Dar{\"u}berhinaus besitzen PPA1 und PPB1 biologische Wirkung. Sie stimulierten beispielsweise die Bildung von Phytoalexinen in mehreren Zellkulturen. Diese Daten implizieren, dass die Bildung von Phytoprostanen eine Folge von oxidativem Stress in Pflanzen ist und dass Phytoprostane pflanzliche Abwehrmechanismen induzieren k{\"o}nnen.},
  subject      = {Pflanzen},
  language  = {de}
}
@phdthesis{Englert2005,
  author    = {Englert, Markus},
  title     = {Mechanismus des pre-tRNA-Spleißens : Struktur und Funktion pflanzlicher und animaler RNA-Ligasen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-14420},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2005},
  abstract  = {Transfer Ribonukleins{\"a}uren werden von der RNA Polymerase III als Vorl{\"a}ufer tRNA transkribiert und durchlaufen eine Vielzahl von Reifungsschritten hin zur maturen tRNA. Neben der Hydrolyse der 5´- und 3´-Flanke durch die RNase P und die tRNase Z, sowie einer Vielzahl von Basenmodifizierungen, wird bei einigen pre-tRNAs das Intron herausgespleißt. Die ersten intronhaltigen tRNA Gene wurden in der Hefe Saccharomyces cerevisiae nachgewiesen und folglich wurde der Spleißmechanismus in diesem Organismus als erstes untersucht. Eine tetramere tRNA Spleißendonuklease spaltet das Intron an den Exongrenzen heraus und eine tRNA Ligase ligiert die entstandenen tRNA H{\"a}lften zur gespleißten tRNA. Einzig in der Hefe und anderen Pilzen konnten bisher die Gene f{\"u}r die tRNA Ligase identifiziert werden. Weder molekularbiologische Ans{\"a}tze - wie z.B. DNA Hybridisierung, Expressions-"Screening" und funktionelle Komplementationsstudien mit einem tRNA Ligase-defizienten Hefestamm - noch Datenbanksuchen mit der bekannten Hefe tRNA Ligasesequenz haben in den vergangenen Jahren zur Identifizierung eines pflanzlichen oder animalen tRNA Ligase Gens gef{\"u}hrt. In dieser Arbeit ist es erstmals gelungen, das tRNA Ligase Protein aus Weizenkeimen bis zur Homogenit{\"a}t zu isolieren und mit Hilfe erhaltener Peptidsequenzen die entsprechenden Kern-codierten Gene in h{\"o}heren und niederer Pflanzen zu identifizieren. Die Ligaseaktivit{\"a}t wurde f{\"u}r das klonierte, rekombinant {\"u}berexprimierte tRNA Ligaseprotein best{\"a}tigt. Weiterhin wurde zum ersten Mal das Ligaseprotein aus Schweineleber aufgereinigt und das zugeh{\"o}rige Gen im humanen Genom identifiziert.},
  subject      = {Pflanzen},
  language  = {de}
}
@phdthesis{Karg2006,
  author    = {Karg, Kathrin},
  title     = {Analyse biologisch aktiver, oxidierter Lipide in Pflanzen und Menschen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-20424},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {Durch freie, radikalkatalysierte Oxidation von Linolens{\"a}ure k{\"o}nnen in vitro und in vivo meh-rere Klassen von Phytoprostanen gebildet werden. Im Rahmen der vorliegenden Arbeit wur-den Phytoprostane in Pflanzenmaterial (Bl{\"a}ttern, Bl{\"u}tenpollen), Speise{\"o}len sowie in mensch-lichen K{\"o}rperfl{\"u}ssigkeiten (Blut und Urinproben) untersucht. Zus{\"a}tzlich wurden neue Metho-den entwickelt, um Phytohormone sowie verschiedene Metabolite des pflanzlichen Prim{\"a}r- und Sekund{\"a}rstoffwechsels zusammen mit einer gemeinsamen Aufarbeitung erfassen und bestimmen zu k{\"o}nnen. Bl{\"u}tenpollen enthalten mehrere mmol/g an Phytoprostanen, darunter PPA1/PPB1, PPE1 und PPF1. Physiologisch relevant sind jedoch nur die Mengen, die sich nach Extraktion in einem w{\"a}ssrigen Puffer wiederfinden lassen. Deshalb wurden hier erstmals w{\"a}ssrige Extrakte von Birkenpollen untersucht. In diesen befanden sich durchschnittlich 60 nmol PPE1 und 10 nmol PPF1 pro g extrahiertem Pollen. Pflanzen{\"o}le enthalten a-Linolens{\"a}ure bis zu einem Gewichtsanteil von 56 \% (m/m). In Spei-se{\"o}len aus ausgesuchten Pflanzenarten (Lein{\"o}l, Soja{\"o}l, Oliven{\"o}l), Walnuss{\"o}l, Traubenkern{\"o}l) und parenteraler Nahrung (Intralipid) wurden die Phytoprostanklassen A1, B1, D1, E1, F1 und deoxy-J1 nachgewiesen und quantifiziert. In frischen {\"O}len wurden große Mengen an Phy-toprostanen (0,4 - 101 mg/g {\"O}l) gefunden, welche teilweise frei und teilweise verestert vorla-gen. Der absolute Phytoprostangehalt der {\"O}le nahm in folgender Reihe ab: Lein{\"o}l » Soja{\"o}l > Oliven{\"o}l > Walnuss{\"o}l > Raps{\"o}l >> Traubenkern{\"o}l. (a-Tocopherol). In allen untersuchten {\"O}-len dominierten entweder PPE1 oder PPF1 als h{\"a}ufigste Phytoprostanklasse. PPA1 und PPB1 waren lediglich als untergeordnete Bestandteile enthalten. PPD1 und dPPJ1 konnten nur in sehr geringen Mengen gefunden werden. Wenn ein {\"O}l bei l{\"a}ngerer Lagerung autoxidiert, k{\"o}nnen die Gehalte an oxidierten Fetts{\"a}uren um ein Vielfaches ansteigen. Es konnte gezeigt werden, dass bei der Autoxidation von Spei-se{\"o}len weitere Phytoprostane entstehen und die Konzentrationen von PPE1 und PPF1 im {\"O}l bis auf das 10-fache ansteigen k{\"o}nnen. Weiterhin wurde dabei die Bildung von detektierbaren Mengen dPPJ1 nachgewiesen. Die Kinetik der Phytoprostanbildung folgte dem f{\"u}r andere Autoxidationsprodukte typischem zeitlichen Verlauf und erst nach {\"U}berschreiten einer Induk-tionsperiode traten vermehrt Phytoprostane auf. Im menschlichen Verdauungstrakt sind Phytoprostane chemisch stabil. Allerdings k{\"o}nnen im sauren Milieu des Magens (pH 0-2) Dehydratisierungen auftreten: Nach Inkubation von PPE1 in 0,1 M HCl waren nach 3 h noch 97 \% intakt, wohingegen 3 \% nichtenzymatisch zu PPA1 konvertiert waren. Unter den gleichen Bedingungen wurden 19 \% der inkubierten PGD1 zu dPGJ1 dehydratisiert. In den Pflanzen{\"o}len veresterte PPF1 wurden mit Schweinepankreas-Lipase innerhalb 1 h zu 44 bis 100 \% hydrolysiert. Raffinierte Speise{\"o}le, welche fast ausschließlich aus Triacylglyce-riden zusammengesetzt sind, wurden die veresterten PPF1 sogar zu fast 100 \% hydrolysiert. Weiterhin konnte erstmals gezeigt werden, dass Phytoprostane nach oraler Aufnahme resor-biert werden k{\"o}nnen und anschließend mit dem Urin ausgeschieden werden. Nach Verzehr von Pflanzen{\"o}len (Soja{\"o}l, Oliven{\"o}l, Traubenkern{\"o}l) wurden die Spiegel von PPF1 in Blut und Urin bestimmt. Dabei zeigte sich eine deutliche Korrelation zwischen dem Phytoprostangehalt der {\"O}le und dem Gehalt in den Blut- und Urinproben: Nach Konsum von Oliven- oder Soja{\"o}l konnten innerhalb von 24 h PPF1 in Blut und Urin wiedergefunden werden, wohingegen der Konsum von Traubenkern{\"o}l in den untersuchten Zeitr{\"a}umen weder im Blut noch im Urin zu detektierbaren PPF1-Mengen f{\"u}hrte. Im Blut lag PPF1 verestert vor: Im Serum von Oliven{\"o}l-Konsumenten konnten durchschnittlich 1,22 nmol/l PPF1 gefunden werden. Das Serum eines Soja{\"o}l-Konsumenten enthielt 0,97 nmol PPF1/l. Die Ausscheidung von unmetabolisierten PPF1 mit dem Urin erfolgte fast vollst{\"a}ndig innerhalb der ersten 8 h nach dem Konsum der {\"O}le, 8 bis 24 h danach konnten im Urin nur noch sehr geringe Mengen PPF1 detektiert wer-den. In den Urinproben der Konsumenten von Oliven{\"o}l oder Soja{\"o}l konnten nach 0-4 h durch-schnittlich 2,02 bzw. 0,43 pmol PPF1/mg Kreatinin und nach 4-8 h 1,39 bzw. 0,68 pmol PPF1/mg Kreatinin gefunden werden. Im Rahmen dieser Arbeit wurde eine Methode entwickelt, welche die simultane Bestimmung von Phytohormonen, Oxylipinen und Fetts{\"a}uren erm{\"o}glicht. Weiterhin wurden Methoden zur Metabolit-Analytik entwickelt, mit welchen Konzentrationsunterschiede zwischen zwei Pro-ben direkt verglichen werden k{\"o}nnen. Zur Markierung von der Carboxylgruppe von Oxylipinen, Phytohormonen und Aminos{\"a}uren mit 18O-Sauerstoff wurden allgemein anwendbare Methoden entwickelt. Die [18O]2-markierten Verbindungen erwiesen sich als stabil und eigneten sich als interner Standard in der GC-MS und HPLC-MS Analytik.},
  subject      = {Prostaglandine},
  language  = {de}
}
@phdthesis{Gupta2007,
  author    = {Gupta, Kapuganti Jagadis},
  title     = {Nitric oxide in plants: Investigation of synthesispathways and role in defense against avirulent Pseudomonas},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-25545},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2007},
  abstract  = {Die Zahl der physiologischen Prozesse in Pflanzen, die scheinbar durch NO reguliert werden, hat in den letzten Jahren stark zugenommen. NO {\"u}bernimmt wichtige Rollen f{\"u}r die Steuerung von Wachstum und Entwicklung, f{\"u}r die Pathogenresistenz und bei abiotischem Stress, sowohl in unterirdischen als auch in oberirdischen Organen. In Pflanzen wurden bisher eine Reihe verschiedener enzymatischer und einige wenige nichtenzymatische Synthesewege f{\"u}r NO vorgeschlagen. Das Hauptziel dieser Arbeit bestand nun darin, die NO Produktion von Pflanzen und speziell von Wurzeln m{\"o}glichst quantitativ zu erfassen und die beteiligten Enzyme zu identifizieren. Dieses Ziel sollte vor allem durch Chemilumineszenz-Messung von NO in der Gasphase (= direkte Chemilumineszenz) erreicht werden, aber auch durch die indirekte Chemilumineszenz, bei welcher Spuren von NO-Oxidationsprodukten wie Nitrat und Nitrit erfasst werden. Als Versuchspflanzen wurden verwendet: Wildtypen von Nicotiana tabacum cv. Xanthi oder cv. Gatersleben; Nitratreduktase-freie, auf Ammonium-N angezogene Mutanten, die keine Nitratreduktase (NR) induzieren; WT Pflanzen, die auf Wolframat angezogen wurden um die Synthese funktionaler MoCo-Enzyme zu unterbinden; eine NO-{\"u}berproduzierende, Nitritreduktase (NiR)-freie Transformante, sowie gelegentlich Gerste, Reis und Erbsen. Eine hypersensitive Reaktion (HR) von Tabak wurde erzeugt durch Druckinfiltration von avirulenten Bakterien des Stammes Pseudomonas syringae pv. phaseolicola. Bei Sauerstoffkonzentrationen \&\#8804;1\% wurde exogenes Nitrit auch von v{\"o}llig NR-freien Wurzeln zu NO reduziert. Folglich war NR nicht die einzige NO-Quelle von Wurzeln. Im Gegensatz dazu waren NR-freie Blattstreifen nicht in der Lage, Nitrit zu NO umzusetzen. Die NO-Bildung von Wurzeln wurde außerdem durch Hemmstoffe des mitochondrialen Elektronentransportes, Myxothiazol und Salicylhydroxams{\"a}ure (SHAM) gehemmt, w{\"a}hrend die NO-Produktion von NR-exprimierenden Blattstreifen gegen diese Inhibitoren unempfindlich war. Damit stimmte auch {\"u}berein, dass gereinigte Mitochondrien aus Wurzeln, aber nicht die aus Bl{\"a}ttern Nitrit mit Hilfe von NADH zu NO reduzieren konnten. Die Inhibitor-Wirkung l{\"a}sst darauf schließen, dass in Wurzelmitochondrien beide terminalen Oxidasen and der NO-Bildung beteiligt sind, und dass selbst in NR-haltigen Wurzeln ein großer Teil der Reduktion von Nitrit zu NO durch die Mitochondrien bewerkstelligt wird, und weniger durch NR selbst. Die Unterschiedliche F{\"a}higkeit von Blatt-und Wurzelmitochondrien zur anaeroben Nitrit:NO-Reduktion wurde nicht nur bei Tabak, sondern auch bei Arabidopsis, Gerste und Erbse gefunden. Sie scheint also eine generelle Eigenschaft h{\"o}herer Pflanzen zu sein. Die Nitrit:NO Reduktion wurden auch direkt als Nitrit- bzw. NADH-Verbrauch gemessen. Die Reaktion war außerdem exklusiv mit der Membranfraktion der Mitochondrien assoziert, ohne jede Beteiligung von Matrixkomponenten. Es wurde auch gepr{\"u}ft, ob Wurzelmitochondrien und- gereinigte Membranen NO ausschließlich aus Nitrit produzierten, oder eventuell auch {\"u}ber eine NO-Synthase (NOS). Außerdem wurde untersucht, ob und in welchem Umfang die NO-Messungen durch eine NO-Oxidation verf{\"a}lscht werden konnten. Zus{\"a}tzlich zur Chemilumineszenz wurden Fluoreszenzmessungen mit Diaminofluoreszeinen (DAF) zum Vergleich herangezogen. In Luft produzierten Mitochondrien ja kein Nitrit-abh{\"a}ngiges NO, und eine NOS-Aktivit{\"a}t konnte weder durch direkte noch durch indirekte Chemilumineszenz nachgewiesen werden. Mit DAF-2 oder DAR-4M wurde jedoch eine L-Arginin-abh{\"a}ngige Fluoreszenzerh{\"o}hung beobachtet. Diese scheinbare NOS-Aktivit{\"a}t wurde mit kommerzieller iNOS verglichen und zeigte dabei sehr untypische Antworten auf NOS-Inhibitoren, Substrate und Kofaktoren. Sie wird deshalb als Artefakt beurteilt. Bei Verwendung von iNOS wurden ca. 2/3 des insgesamt produzierten NO zu (Nitrit+Nitrat) oxidiert. Mitochondrien scheinen NO zu verbrauchen, ohne jedoch die Oxidation von NO zu (Nitrit+Nitrat) zu erh{\"o}hen. Vermutlich wird dabei ein fl{\"u}chtiges Intermediat gebildet (eventuell N2O3). In unserer Gruppe wurde k{\"u}rzlich gezeigt, dass der pilzliche Elicitor Cryptogein eine hypersensitive Reaktion (HR) bei Tabak hervorrief, die v{\"o}llig unabh{\"a}ngig von der Gegenwart oder Abwesenheit von NR war. Eine Schlussfolgerung daraus war, dass die NR-abh{\"a}ngige NO-Bildung f{\"u}r die HR keine Rolle spielte. Hier pr{\"a}sentieren wir Hinweise darauf, dass dieses Szenario Cryptogein-spezifisch sein k{\"o}nnte. Pseudomonas syringae pv phaseolicola wurde in Tabakbl{\"a}tter des Wildtyps und derNiR-defizienten, NO-{\"u}berproduzierenden Mutante (clone 271) infiltriert, die entweder auf Ammonium oder auf Nitrat angezogen waren. Es wurde die Entwicklung der L{\"a}sionen, das Bakterienwachstum und die Zuckerkonzentrationen in den Bl{\"a}ttern und im Blattapoplasten verfolgt. Die L{\"a}sionen-Entwicklung war positiv, und das Bakterienwachstum negativ korreliert mit der Nitrat-Ern{\"a}hrung und einer eventuellen NO-Produktion. Das Bakterienwachstum war positiv korreliert mit einer Ammonium-Ern{\"a}hrung und mit apoplastischen Zuckerkonzentrationen. Der Gesamtgehalt an freier + konjugierter Salicyls{\"a}ure (SA) war durch bakterielle Infektion immer drastisch gesteigert, aber ohne klare Korrelation mit einer NO-Produktion. In Gegenwart von Cryptogein war das Wachstum von Pseudomonas fast v{\"o}llig gehemmt. Diese Beobachtungen deuten darauf hin, dass die vermutete gegenseitige Abh{\"a}ngigkeit von Bakterienwachstum, NO-Produktion und der HR sehr komplex ist und nicht auf einfache unifaktorielle Beziehungen reduziert werden kann.},
  subject      = {Pflanzen},
  language  = {en}
}
@phdthesis{Kuhlmann2009,
  author    = {Kuhlmann, Franziska},
  title     = {The influence of ultraviolet radiation on plant-insect interactions},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39608},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {Plants must respond to multiple stimuli in a natural environment. Therefore they need the ability to rapidly reorganise and specifically build up appropriate metabolites to adapt to their environment. Abiotic cues, such as ambient solar radiation, influence the next trophic level directly, but also an altered plant composition triggered by these environmental cues can have an effect on the behaviour of herbivores. The aim of this study was to test effects of the important ultraviolet (UV) radiation on plants and on plant-insect interactions using multi-level investigations. The focus was on the conduction of controlled experiments with broccoli plants in highly engineered greenhouses covered with innovative materials, which only differed in their UV-B transmission. For the first time in this controlled environment the plant-mediated UV-B effects on phloem-feeding aphids were studied. Broccoli plants (Brassica oleracea L. convar. botrytis, Brassicaceae) were under filter tents either exposed to (inclusion, +UV) or not exposed to (exclusion, -UV) UV-A / UV-B radiation. In greenhouses covered with new, innovative materials transmitting high (80\%), medium (23\%) or low (4\%) levels of ambient solar UV-B radiation, in particular the influence of UV-B radiation on broccoli was examined. Plants respond highly specific to environmental stimuli such as UV-B radiation and herbivory. UV-B radiation has a strong impact on the plants' architecture and flavonoid contents, which can in turn influence plant-insect interactions. Phloem-feeding aphids can be negatively affected by UV-B mediated plant changes. However, a direct effect of UV radiation on the behaviour of herbivores is also evident. Mainly the number, composition and quality of herbivorous species as well as an exceeding of a certain infestation threshold determine the mode of plant changes. In conclusion, UV-B radiation has the potential to harden plants against herbivores and simultaneously increases the concentrations of valuable secondary metabolites for human nutrition in important crop species such as broccoli.},
  subject      = {ultraviolette Strahlung},
  language  = {en}
}
@phdthesis{Schaefer2012,
  author    = {Sch{\"a}fer, Barbara},
  title     = {Untersuchungen zur Regulation der Invertaseaktivit{\"a}t und zu Invertaseinhibitoren aus Pflanzenextrakten},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-71469},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Die Spaltung verschiedener Zuckerverbindungen ist ein elementarer Vorgang in allen Lebewesen. Im Rahmen dieser Arbeit wurden Enzyme untersucht, die Saccharose, einen wichtigen Energietr{\"a}ger und Botenstoff, in Fructose und Glucose spalten. Sie liefert einen umfassenden {\"U}berblick saccharosespaltender Enzyme und deren Inhibitoren, der erstmals die Gebiete der β-Fructofuranosidasen und der α-Glucosidasen vereinigt. Invertasen (β-Fructofuranosidasen, Abspaltung der Fructose) spielen eine zentrale Rolle im Metabolismus der Pflanzen und werden auf vielf{\"a}ltige Art und Weise reguliert. Im Rahmen dieser Arbeit wurden Ver{\"a}nderungen in der Aktivit{\"a}t durch verschiedene Einfl{\"u}sse in vitro untersucht. Dabei konnte gezeigt werden, dass die Temperaturoptima der Invertasen erstaunlich hoch liegen. Das Verhalten der getesteten alkalischen / neutralen Invertase aus Lolium temulentum unterschied sich bei vielen Tests von dem der anderen eingesetzten Invertasen. Auch in Tieren bzw. im Menschen sind saccharosespaltende Enzyme, hier bezeichnet als Sucrasen bzw. α-Glucosidasen (Abspaltung der Glucose), an vielen wichtigen Vorg{\"a}ngen beteiligt, etwa der Glykosilierung von Proteinen oder der Verdauung. Die humane Sucrase-Isomaltase aus dem D{\"u}nndarm ist ein Target in der Diabetestherapie. Erstmals konnte die humane Sucrase als aktive Untereinheit in der Hefe Pichia pastoris exprimiert werden. Neben den Enzymen selbst wurden das Wirkspektrum und die Wirkst{\"a}rke verschiedener Inhibitoren untersucht. Dabei konnte festgestellt werden, dass Acarbose, ein Pseudotetrasaccharid, das in der Diabetestherapie verwendet wird, auch pflanzliche Invertasen hemmt. Die in ihrer Struktur zueinander sehr {\"a}hnlichen Iminozucker DMDP, Miglitol und Calystegin B2 unterschieden sich erheblich in ihrer Hemmaktivit{\"a}t. DMDP ist dabei am potentesten, Miglitol f{\"u}hrt teilweise zu einer erh{\"o}hten Invertaseaktivit{\"a}t und Calystegin B2 verf{\"u}gt nur {\"u}ber ein beschr{\"a}nktes Hemmspektrum. Pflanzliche proteinogene Invertaseinhibitoren hemmten auch die humane Sucrase und die Hefeinvertase; wurden die Inhibitorproteine in P. pastoris exprimiert und dabei glykosiliert, hatten sie keine Hemmaktivit{\"a}t. Als einziger Inhibitor zeigte Miglitol der getesteten alkalischen / neutralen Invertase gegen{\"u}ber ein Verhalten, das als selektiv bezeichnet werden kann, da die Hemmung mit Konzentrationen, die um den Faktor 1000 niedriger waren als bei anderen Invertasen, eintrat. F{\"u}r die Suche nach neuen Inhibitoren wurden ein Screening und eine Literaturrecherche zum Thema Pflanzen in der Diabetestherapie bzw. pflanzliche Glucosidasehemmstoffe durchgef{\"u}hrt. Die Literaturrecherche weist darauf hin, dass eine große Anzahl an Pflanzen potentielle Wirkstoffe beinhalten k{\"o}nnte. Das Screening nach neuen Hemmstoffen wurde gr{\"o}ßtenteils mit Pflanzenextrakten aus der Traditionellen Chinesischen Medizin durchgef{\"u}hrt. Dabei wurden hemmende Extrakte entdeckt, die weiter auf ihre aktiven Komponenten hin untersucht werden sollten.},
  subject      = {Invertase},
  language  = {de}
}
@phdthesis{Stangl2012,
  author    = {Stangl, Christoph},
  title     = {Lichtgesteuerte Manipulation Zentraler Second Messenger in Pflanzen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-85940},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {In der vorliegenden Arbeit wurden lichtaktivierte Nucleotidcyclasen auf Basis der lichtaktivierten Adenylatcyclase bPAC (=BlaC, Ryu et al., 2010; Stierl et al., 2011), sowie der direkt lichtaktivierbare Kationenkanal Channelrhodopsin-2 (Nagel et al., 2003) eingesetzt, um lichtinduzierte und damit nicht-invasive Manipulationen der Second Messenger cAMP, cGMP und Calcium, sowie des Membranpotentials in Pflanzenzellen vorzunehmen. Nach transienter Transfektion von N. benthamiana konnte sowohl die Expression der beiden Channelrhodopsinvarianten C128A::YFP und C128T::YFP (unver{\"o}ffentlichte Daten von R. Gueta und G. Nagel, 2008, Berndt et al., 2009; Bamann et al., 2010), als auch deren Lokalisation in der Plasmamembran von Protoplasten fluoreszenzmikroskopisch gezeigt werden. Die Funktion von Channelrhodopsin als lichtaktivierbarer Kationenkanal konnte in dieser Arbeit erstmals elektrophysiologisch in Pflanzenzellen nachgewiesen werden. In Einstichmessungen im Mesophyllgewebe von N. benthamiana wurden reproduzierbar blaulichtinduzierte Depolarisationen der Plasmamembran erzielt, die in Dauer und Frequenz {\"u}ber das applizierte Lichtmuster steuerbar waren. In Patch-Clamp-Messungen an epidermalen Protoplasten von N. benthamiana, welche transient Channelrhodopsin-2-C128A und Channelrhodopsin-2-C128T exprimierten, konnten zudem blaulichtinduzierte Einw{\"a}rts-Str{\"o}me gezeigt werden. Die Expression der beiden verwendeten Channelrhodopsinvarianten schien hierbei ann{\"a}hernd unabh{\"a}ngig von der vorliegenden Konzentration des zugegebenen Retinals. Des Weiteren konnte in A. thaliana sowohl die Expression als auch die Funktion der lichtaktivierbaren Adenylatcyclase bPAC::YFP (Stierl et al., 2011), sowie einer hieraus durch gezielte Mutation (nach Ryu et al., 2010) abgeleiteten lichtaktivierbaren Guanylatcyclase (bPGC::YFP) erstmalig in h{\"o}heren Pflanzen gezeigt werden. Nach Best{\"a}tigung der Funktion dieser beiden lichtaktivierbaren Nucleotidcyclasen in transient transfizierten Protoplasten von A. thaliana wurden zwei stabil transgene Pflanzenlinien generiert. ZUSAMMENFASSUNG DER ARBEIT - 190 - Pflanzen dieser Linie exprimierten neben dem konstitutiv unter der Kontrolle des 35S-CaMV-Promotors exprimierten Calciumreporterprotein Aequorin zus{\"a}tzlich und unter der Kontrolle eines {\"o}strogeninduzierbaren Glucocorticoidpromotors (Zuo et al., 2000) die lichtaktivierten Nucleotidcyclasen bPAC::YFP bzw. bPGC::YFP. In beiden stabil transgenen Pflanzenlinien wurden Expression und Funktion der jeweiligen lichtaktivierten Nucleotidcyclase gezeigt. In Messungen an einem modifizierten Luminometer konnten weiterhin erstmals blaulichtinduzierte Calciumsignaturen in Pflanzenzellen generiert werden. Auf die Folge von Blaulichtpulsen kam es wiederholt zum Calciumeinstrom in Zellen der erstellten transgenen Pflanzenlinien. Neben der M{\"o}glichkeit, sowohl die Konzentration der cyclischen Nucleotide als auch des cytoplasmatischen Calciums {\"u}ber Licht zu manipulieren, wurde durch diese Pflanzen ein direkter Zusammenhang beider Second Messenger gezeigt. Weiterhin sind ph{\"a}notypische Auff{\"a}lligkeiten der erstellten Pflanzenlinien beobachtet worden. Es kam zur Verz{\"o}gerung des Keimungszeitpunktes bPAC::YFP-exprimierender Samen im Licht, jedoch wuchsen die Pflanzen im Anschluss an die verz{\"o}gerte Keimung normal und uneingeschr{\"a}nkt weiter. In bPAC::YFP-exprimierenden Pollen von Nicotiana SR-1 konnte zudem das Wachstum der Pollenschl{\"a}uche durch blaues Licht gestoppt werden. bPGC::YFP-exprimierende Pollen hingegen zeigten auch im blauen Licht unver{\"a}ndertes Pollenschlauchwachstum. Neben den beiden erfolgreich generierten, stabil transgenen Pflanzenlinien wurden in analogen Ans{\"a}tzen transgene A. thaliana Col-0 Aequorin Zellkulturlinien generiert, die neben dem konstitutiv aktiven Calciumreporterprotein Aequorin ebenso bPAC::YFP bzw. bPGC::YFP unter der Kontrolle des {\"o}strogeninduzierbaren Glucocorticoidpromotors (Zuo et al., 2000) exprimierten. Auch hier konnten Expression und Funktion beider Nucleotidcyclasen immunologisch und fluoreszenzmikroskopisch gezeigt werden. {\"U}ber den Einsatz einer sog. 2A-Sequenz wurde weiterhin ein funktionsf{\"a}higes Fusionskonstrukt aus dem cAMP-aktivierten Kationenkanal CNGA2 (C460W-E583M, nach Rich et al., 2001) und der lichtaktivierten Adenylatcyclase EuPACα (Iseki et al., 2002) erstellt. Die Funktion dieses Fusionskonstruktes wurde elektrophysiologisch sowie immunologisch gezeigt.},
  subject      = {Calciumion},
  language  = {de}
}
@phdthesis{Baumann2013,
  author    = {Baumann, Melanie},
  title     = {Optogenetische Simulation und Analyse elektrischer und Calcium-basierter Signale in Pflanzen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-87974},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {Funktionelle Expression von ChR2 in Pflanzen In der vorliegenden Arbeit konnte erstmalig die funktionelle Expression des licht-aktivierten Channelrhodopsin-2 aus Chlamydomonas reinhardtii in h{\"o}heren Pflanzen gezeigt werden. Obwohl die erfolgreiche Transformation auf der Basis der Integration einer Expressionskassette f{\"u}r WT-ChR2 in Pflanzen genetisch nachgewiesen werden konnte, war ein funktioneller Nachweis nicht m{\"o}glich. Demgegen{\"u}ber war die funktio-nelle Expression aller getesteten ChR2-Mutanten im transienten Expressionsansatz er-folgreich und konnte schließlich auf der Basis der im Rahmen dieser Arbeit generierten Konstrukte auch f{\"u}r stabil transformierte Arabidopsis-Pflanzen best{\"a}tigt werden. ChR2 wurde in Arabidopsis-Protoplasten sowie Tabak-Epidermis- und Mesophyllzellen an der Plasmamembran lokalisiert, zeigte jedoch aufgrund der {\"U}berexpression eine starke {\"U}berladung des Endomembransystems. Elektrophysiologische Messungen mit Hilfe der Einstichtechnik belegten, dass ChR2 sowohl in Arabidopsis-Keimlingen als auch im Tabakmesophyll funktionell ist, wobei sich die erzeugten Blaulicht-vermittelten Depolarisationen weitaus erfolgreicher im Ta-baksystem darstellten. Alle eingesetzten ChR2-Mutanten waren funktionell und zeigten in Einstichmessungen mit Oozytendaten korrelierende Kinetiken. Die Mutante C128A wurde hinsichtlich der erzielten lichtinduzierten Membranpotentialdepolarisationen als effektivste ChR2-Variante identifiziert. Calcium-Messungen mit dem Reporterprotein Aequorin lieferten keinen Beweis f{\"u}r einen direkt durch ChR2-C128A vermittelten Calcium-Einstrom in Arabidopsis-Protoplasten. Jedoch konnte ein cytosolischer Calcium-Anstieg ca. 3min nach Blau-lichtapplikation beobachtet werden. Dies deutet darauf hin, dass die durch ChR2 vermittelten Membranpotential{\"a}nderungen zu einer Aktivierung endogener, Calcium-permeabler Ionenkan{\"a}le f{\"u}hren k{\"o}nnte. F{\"u}r die ChR2-L132C Mutante konnte allerdings in ersten Messungen ein direkter Calcium-Anstieg nach Lichtgabe beobachtet werden.   Transkriptionelle {\"A}nderungen aufgrund ChR2-basierter, elektrischer Signalmuster In RNA-Seq-Analysen mit transient transformierten Tabakbl{\"a}ttern konnte die Bedeu-tung der Signalsignatur elektrischer bzw. Calcium-basierter Signale verifiziert werden: Die Applikation zweier in ihrer Form g{\"a}nzlich unterschiedlicher elektrischer Signal-muster lieferte ein signifikant unterschiedlich reguliertes Set an Genen, wobei einige wenige durch beide Behandlungen induziert werden konnten. Langanhaltende Depolari-sationen regulierten deutlich mehr Gene und waren daher in ihrer Wirkung weitaus ef-fektiver als kurze, repetitive Depolarisationen. Die bioinformatische Analyse dieser Daten zeigte, dass die Nachahmung eines im Zuge der Pathogenantwort bekannten, langen Depolarisationspulses Gene der Flagellin-induzierten Signaltransduktion adressierte, w{\"a}hrend kurze, wiederkehrende Pulse mit gleichem Informationsgehalt diese nicht regulierten.},
  subject      = {Channelrhodopsin-2},
  language  = {de}
}
@phdthesis{Ruemer2013,
  author    = {R{\"u}mer, Stefan},
  title     = {Untersuchungen zur oxidativen Bildung von Stickstoffmonoxid in Pflanzen sowie zur Visualisierung von Stickstoffmonoxid mittels Fluoreszenzfarbstoffen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-77115},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {Stickstoffmonoxid (NO) ist ein gasf{\"o}rmiges, relativ stabiles Radikal, das in Pflanzen u. a. durch Reduktion aus Nitrit unter Katalyse des Enzyms Nitratreduktase gebildet wird. In tierischen Organismen wird NO dagegen {\"u}ber einen oxidativen Syntheseweg aus der Ami-nos{\"a}ure L-Arginin katalysiert durch verschiedene Isoformen der NO-Synthasen (NOS) hergestellt. Es besitzt im tierischen System vielf{\"a}ltige Funktionen u. a. als Neurotransmitter sowie Blutfluss und -druck regulierendes Agens. Im Pflanzenreich werden NO u. a. Aufgaben bei der Regulierung von Spalt{\"o}ffnungen, der Abwehr von Pathogenen sowie der Differenzierung der Xylemelemente zugeschrieben. Die vorliegende Arbeit verfolgte zwei Ziele: - Erforschung alternativer oxidativer Synthesewege von NO in Pflanzen und - Untersuchung der NO-Spezifit{\"a}t der DAF-Fluoreszenzfarbstoffe ausgehend Diskrepanzen zwischen Daten aus Floureszenzanalysen und der Gasphasen-Chemilumineszenz in fr{\"u}heren Arbeiten unserer Arbeitsgruppe und zahlreichen weiteren Publikationen. a) NO-Produktion aus Hydroxylaminen Hydroxylamin ist ein Zwischenprodukt bei der bakteriellen Denitrifizierung und wurde auch als Intermediat bei der Nitratreduktion in Pflanzen diskutiert. Hier wird gezeigt, dass Tabaksuspensionzellen in der Lage waren, exogenes Hydroxylamin schon in sehr niedrigen Konzentrationen (4 µM) zu NO zu oxidieren. Auch ein anderes HA-Derivat, n{\"a}mlich der Hemmstoff der Alternativen Oxidase (AOX) in Mitochondrien, Salicylhydroxams{\"a}ure (SHAM), wurde zu NO oxidiert. Die Vermutung, reaktive Sauerstoffspezies (ROS) k{\"o}nn-ten bei diesem Oxidationsprozess eine Rolle spielen, wurde {\"u}berpr{\"u}ft: Nach Einwirkung des ROS-abbauenden Enzyms Superoxid-Dismutase (SOD) konnte aber {\"u}berraschender-weise keine Verminderung, sondern eher eine Steigerung der NO-Emission beobachtet werden. Die Rolle der SOD in diesem Reaktionsprozess ist daher noch nicht verstanden. b) NO-Detektion mittels Fluoreszenzindikatoren Zur Visualisierung und Lokalisierung von NO in tierischen und pflanzlichen Zellen und Geweben (in situ) mittels mikroskopischer (LSM) oder fluorimetrischer Methoden werden Fluoreszenzfarbstoffe, z. B. DAF-2 oder DAF-FM verwendet. Diese Farbstoffe reagieren mit NO zu stark fluoreszierenden Triazol-Derivaten. Eine Situation, in der Pflanzen u. a. mit NO-Freisetzung reagieren, ist der Pathogenbefall. Wir untersuchten die Reaktion von Tabaksuspensionszellen auf den pilzlichen Elicitor Cryptogein, ein Protein des Oomyceten Phytophthora cryptogea. Im Filtrat der Zellen, die mit Cryptogein behandelt wurden, zeigte sich nach Zugabe von DAF-Farbstoffen ein starker Fluoreszenzanstieg. Um die fluoreszenzerh{\"o}henden Stoffe zu charakterisieren, wurde das Filtrat vor der DAF-Zugabe verschiedentlich behandelt. Bei Zugabe von KCN bzw. Katalase zum {\"U}berstand, verringerte sich der Fluoreszenzanstieg. Gleichzeitige Behandlung der Zellen mit Cryptogein sowie dem NADPH-Oxidase-Inhibitor DPI unterband den Fluoreszenzanstieg im {\"U}berstand nahezu komplett. Enzym-Assays mit Amplex Rot zeigten die Anh{\"a}ufung von H2O2 im Filtrat der elicitierten Zellen. Neben ROS werden von Pflanzenzellen auch Peroxidasen in den Apoplasten sekretiert, die mit Hilfe von H2O2 f{\"u}r eine verst{\"a}rkte Quervernetzung der Zellwand sorgen. Sowohl in unbehandelten Kontrollzellen als auch in elicitierten Zellen wurde Peroxidase-Aktivit{\"a}t nachgewiesen. Nach Zugabe von H2O2 und DAF-2 zum Filtrat von Kontrollzellen ergab sich ein Fluoreszenzanstieg {\"a}hnlich dem im Filtrat von behandelten Zellen. Mit Hilfe eines einfachen In-vitro-Systems aus Meerettich-Peroxidase (MR-PO), Wasser-stoffperoxid (H2O2) und DAF-2 konnten noch h{\"o}here Fluoreszenzwerte erzielt werden, was die Vermutung der Fluoreszenzerh{\"o}hung ohne Anwesenheit von NO erh{\"a}rtete. Um diese nicht aus einer Reaktion mit NO resultierenden DAF-Produkte n{\"a}her zu charak-terisieren, wurden Trennungen mittels Umkehrphasen-Hochdruck-Fl{\"u}ssigkeitschro-matographie mit Fluoreszenzdetektion (RP-HPLC-FL) und Massenspektrometrie (UPLC-MS) durchgef{\"u}hrt. Dabei wurden tats{\"a}chlich zwei neue Reaktionsprodukte festgestellt, die sich eindeutig von DAF-2T unterschieden. Letzteres konnte nur bei Hinzuf{\"u}gen des NO-Donors DEA-NO detektiert werden. Zur Erfassung von intrazellul{\"a}ren Reaktionsprodukten von DAF wurden die chromatogra-phischen Trennmethoden auch auf Extrakte von mit DAF-2 DA aufgeladenen und danach elicitierten Zellen angewandt. Bei dieser Auftrennung tauchten noch mehr DAF-Reaktionsprodukte auf. Die Hauptfluoreszenz, die auch bei nicht inkubierten Zellen auf-trat, konnte auf eine Reihe sehr fr{\"u}h eluierender Substanzen zur{\"u}ckgef{\"u}hrt werden. Die zwei DAF-Derivate aus dem {\"U}berstand inkubierter Zellen bzw. der In-vitro-Reaktion (MR-PO+H2O2+DAF-2) tauchten jedoch {\"u}berhaupt nicht auf. Vorl{\"a}ufige massenspektrometrische Analysen legen nahe, dass es sich bei den in Abwe-senheit von NO gebildeten zwei Verbindungen um isomere Dimere von DAF-2 handelt.},
  subject      = {Stickstoffmonoxid},
  language  = {de}
}
@phdthesis{Leingaertner2013,
  author    = {Leing{\"a}rtner, Annette},
  title     = {Combined effects of climate change and extreme events on plants, arthropods and their interactions},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-87758},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {I. Global climate change directly and indirectly influences biotic and abiotic components of ecosystems. Changes in abiotic ecosystem components caused by climate change comprise temperature increases, precipitation changes and more frequently occurring extreme events. Mediated by these abiotic changes, biotic ecosystem components including all living organisms will also change. Expected changes of plants and animals are advanced phenologies and range shifts towards higher latitudes and altitudes which presumably induce changes in species interactions and composition. Altitudinal gradients provide an optimal opportunity for climate change studies, because they serve as natural experiments due to fast changing climatic conditions within short distances. In this dissertation two different approaches were conducted to reveal species and community responses to climate change. First, species richness and community trait analyses along an altitudinal gradient in the Bavarian Alps (chapters II, III) and second, climate change manipulation experiments under different climatic contexts (chapters IV, V, IV). II. We performed biodiversity surveys of butterfly and diurnal moth species on 34 grassland sites along an altitudinal gradient in the National Park Berchtesgaden. Additionally, we analysed the dominance structure of life-history traits in butterfly assemblages along altitude. Species richness of butterflies and diurnal moths decreased with increasing altitude. The dominance of certain life-history-traits changed along the altitudinal gradient with a higher proportion of larger-winged species and species with higher egg numbers towards higher altitudes. However, the mean egg maturation time, population density and geographic distribution within butterfly assemblages decreased with increasing altitude. Our results indicate that butterfly assemblages were mainly shaped by environmental filtering. We conclude that butterfly assemblages at higher altitudes will presumably lack adaptive capacity to future climatic conditions, because of specific trait combinations. III. In addition to butterfly and diurnal moth species richness we also studied plant species richness in combination with pollination type analyses along the altitudinal gradient. The management type of the alpine grasslands was also integrated in the analyses to detect combined effects of climate and management on plant diversity and pollination type. Plant species richness was highest at intermediate altitudes, whereby the management type influenced the plant diversity with more plant species at grazed compared to mown or non-managed grasslands. The pollination type was affected by both the changing climate along the gradient and the management type. These results suggest that extensive grazing can maintain high plant diversity along the whole altitudinal gradient. With ongoing climate change the diversity peak of plants may shift upwards, which can cause a decrease in biodiversity due to reduced grassland area but also changes in species composition and adaptive potential of pollination types. IV. We set up manipulation experiments on 15 grassland sites along the altitudinal gradient in order to determine the combined effects of extreme climatic events (extreme drought, advanced and delayed snowmelt) and elevation on the nutritional quality and herbivory rates of alpine plants. The leaf CN (carbon to nitrogen) ratio and the plant damage through herbivores were not significantly affected by the simulated extreme events. However, elevation influenced the CN ratios and herbivory rates of alpine plants with contrasting responses between plant guilds. Furthermore, we found differences in nitrogen concentrations and herbivory rates between grasses, legumes and forbs, whereas legumes had the highest nitrogen concentrations and were damaged most. Additionally, CN ratios and herbivory rates increased during the growing season, indicating a decrease of food plant quality during the growing season. Contrasting altitudinal responses of grasses, legumes and forbs presumably can change the dominance structure among these plant guilds with ongoing climate change. V. In this study we analysed the phenological responses of grassland species to an extreme drought event, advanced and delayed snowmelt along the altitudinal gradient. Advanced snowmelt caused an advanced beginning of flowering, whereas this effect was more pronounced at higher than at lower altitudes. Extreme drought and delayed snowmelt had rather low effects on the flower phenology and the responses did not differ between higher and lower sites. The strongest effect influencing flower phenology was altitude, with a declining effect through the season. The length of flowering duration was not significantly influenced by treatments. Our data suggest that plant species at higher altitudes may be more affected by changes in snowmelt timing in contrast to lowland species, as at higher altitudes more severe changes are expected. However, the risk of extreme drought events on flowering phenology seems to be low. VI. We established soil-emergence traps on the advanced snowmelt and control treatment plots in order to detect possible changes in abundances and emergence phenologies of five arthropod orders due to elevation and treatment. Additionally, we analysed the responses of Coleoptera species richness to elevation and treatment. We found that the abundance and species richness of Coleoptera increased with elevation as well as the abundance of Diptera. However, the abundance of Hemiptera decreased with elevation and the abundances of Araneae and Hymenoptera showed no elevational patterns. The advanced snowmelt treatment increased the abundances of Araneae and Hymenoptera. The emergence of soil-hibernating arthropods was delayed up to seven weeks at higher elevations, whereas advanced snowmelt did not influence the emergence phenology of arthropods immediately after snowmelt. With climate change earlier snowmelt will occur more often, which especially will affect soil-hibernating arthropods in alpine regions and may cause desynchronisations between species interactions. VII. In conclusion, we showed that alpine ecosystems are sensitive towards changing climate conditions and extreme events and that many alpine species in the Bavarian Alps are endangered. Many alpine species could exist under warmer climatic conditions, however they are expected to be outcompeted by more competitive lowland species. Furthermore, host-parasite or predator-prey interactions can be disrupted due to different responses of certain guilds to climate change. Understanding and predicting the complex dynamics and potential risks of future climate change remains a great challenge and therefore further studies analysing species and community responses to climate change are needed.},
  subject      = {Insekten},
  language  = {en}
}
@phdthesis{Kartaeusch2015,
  author    = {Kart{\"a}usch, Ralf},
  title     = {Spektroskopische Flussmessung an Pflanzen mittels mobilem Magnetresonanztomographen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125820},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {The main objective of this dissertation was the development of a flow sensor which is specialized on flow measurements of plants. Hence, an accessible mobile magnet and the receiver/transfer hardware have been developed. Additionally, software to control the MR-console has been written. The AC-method was advanced to acquire slow flow profiles. This enables acquiring flow in plants. Additionally, in cooperation with the working group "Lipid Motobolism" of the IPK-Gatersleben studies have been carried out to measure the influence of the ear of wheat on the water transport mechanism. Furthermore, a new technique based on the Bloch-Siegert-effect has been developed which reduces the influence of eddy currents. This simplifies flow measurements that suffer heavily from eddy currents. Hardware development An accessible mobile magnet with a field strength of 0.42 T has been build. The field homogeneity is 0.5 ppm in 1 cm³. In comparison to the existing closed magnet system at the chair EP5 this is an improvement of a factor 40. Those enhancements have been achieved by an adjusted design of the magnet which has been optimized by computer simulations. The implementation of ferrite pole shoes reduced the eddy currents by a factor 7 in comparison to the usually used iron pole shoes. Therefore, phase sensitive flow measurements using fast switching magnet field gradients could be carried out. A foldable coil has been refined to achieve an accessible receiver system. This coil has been used as a transmit/receiver unit. Furthermore, the SNR of measurements in thin plant stalks was enhanced by a constructed system that could be directly wrapped around the stalk. Additionally, two systems to reduce noise in plant measurements have been developed. Those systems can reduce the noise by a factor 92. This was necessary because the longish plant stems guides electric noise from outside of the case into the receiver coil. Both noise reduction systems, the electromagnetic shielding and the common mode rejection, removed the noise to the same level. Flow measurement In the present work a refinement of the AC-method [36] enabled for the first time acquiring quantitative flow profiles. Hence, it was possible to measure slow velocity in the range of 200 µm/s. The precondition was the replacement of the sinusoidal gradient profile by a trapezoid gradient shape. Those allowed increasing the slew rate of the gradients and therefore shorten the total duration of the ramp which finally allows higher encoding strengths. Additionally, due to intervals without applied gradients, more efficient RF-pulses can be used and more data points can be acquired in an echo. The measured flow profiles correlated to the simulation results. The accurate flow profiles have been achieved by a new evaluation technique and a phase correction mechanism. The newly developed extension to imaging enabled spatially encoded spectral flow measurements. Therefore, the location of xylem and phloem can be spatially separated. In the measurement of the black alder this becomes apparent. Here the shape of dicotyledonous plants, which is described in chapter 5.1, is visible. Additionally, due to the spatial separation of the flow directions (up/down) qualitative flow measurements are possible. In pixels where opposite flow directions can spatially be resolved the difference between the left and the right side of the flow spectra yields the total flow without static water. Due to the phase corrections technique in combination with the automatically frequency calibration, long term flow measurements were possible. Therefore, the response of plants on influences like changes in the illumination have been observed in measurements over a duration of nine days. Here flow changes below 200 µm/s can be detected. Bloch-Siegert phase encoding In this work a new spatial phase encoding technique (BS-SET) using a B1-gradient in combination with far off-resonant radio frequency pulses has been demonstrated. Based on the Bloch-Siegert Shift an eddy current free B1-gradient was used to encode images and apply flow encoding. The BS-gradient induces a phase shift which depends on B1² using a constant gradient. Therefore, adapted reconstructions have been developed that provide undistorted images using this nonlinear encoding. Alternatively, a B1-gradient has been developed where the profile of the B1-field follows a square root shape. This supplies a linear phase encoding removing the need for an adapted reconstruction and enables using this technique for flow encoding.},
  subject      = {Kernspintomografie},
  language  = {de}
}
@phdthesis{Munz2018,
  author    = {Munz, Eberhard},
  title     = {Physiological and metabolical high-resolution MRI of plants},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172518},
  school      = {Universit{\"a}t W{\"u}rzburg},
  pages     = {177},
  year      = {2018},
  abstract  = {The noninvasive magnetic resonance imaging technique allows for the investigation of functional processes in the living plant. For this purpose during this work, different NMR imaging methods were further developed and applied. For the localisation of the intrusion of water into the germinating rape seed with the simultaneous depiction of the lipid-rich tissue via a 3D rendering, in Chap. 5 the technique of interleaved chemical selective acquisition of water and lipid was used in the germinating seed. The utilization of high-resolution MR images of germinated seeds enabled the localization of a predetermined water gap in the lipid-rich aleurone layer, which resides directly under the seed coat. The for a long time in biology prevalent discussion, whether such a gap exists or the seed soaks up the water from all sides, rather like a sponge, could hereby, at least for the rapeseed seed, be answered clearly. Furthermore, the segmentation and 3D visualization of the vascular tissue in the rapeseed seeds was enabled by the high-resolution datasets, a multiply branched structure preconstructed in the seed could be shown. The water is directed by the vascular tissue and thus awakens the seed gradually to life. This re-awakening could as well be tracked by means of invasive imaging via an oxygen sensor. In the re-awakened seeds, the lipid degradation starts, other than expected, not in the lipid-rich cotyledons but in the residual endosperm remaining from seed development and in the aleurone layer which previously protected the embryo. Within this layer, the degradation could be verified in the high-resolution MR datasets. The method presented in Chap. 6 provides a further characteristic trait for phenotyping of seeds and lipid containing plants in general. The visualization of the compounds of fatty acids in plant seeds and fruits could be achieved by the distinct utilization of chemical shift-selective imaging techniques. Via the application of a CSI sequence the fatty acid compounds in an olive were localized in a 2D slice. In conjunction with an individually adjusted CHESS presaturation module Haa85 the high-resolution 3D visualization of saturated and unsaturated fatty acid compounds in different seeds was achieved. The ratio maps calculated from these datasets allow to draw conclusions from the developmental stage or the type of seed. Furthermore, it could be shown that the storage condition of two soybean seeds with different storage time durations lead to no degradation of the fatty acid content. Additional structural information from inside of dry seeds are now accessible via MRI. In this work the imaging of cereal seeds could be significantly improved by the application of the UTE sequence. The hitherto existing depictions of the lipid distribution, acquired with the spin echo sequence, were always sufficient for examinations of the lipid content, yet defects in the starchy endosperm or differences in the starch concentration within the seed remained constantly unseen with this technique. In a direct comparison of the datasets acquired with the previous imaging technique (spin echo) and with UTE imaging, the advantage of data acquisition with UTE could be shown. By investigating the potential seed compounds (starch, proteins, sugar) in pure form, the constituent parts contributing to the signal could be identified as bound water (residual moisture) and starch. The application of a bi-exponential fit on the datasets of the barley seed enabled the separate mapping of magnetization and of relaxation time of two components contributing to the NMR signal. The direct comparison with histological stainings verified the previous results, thus this technique can be used for the selective imaging of starch in dry seeds. Conclusions on the translocation characteristics in plants can be drawn by the technique proposed in Chap. 8. The associated translocation velocities can now, even in the range of several um/h, be determined in the living plant. Based on calculated concentrations of an MR contrast agent, which was taken up by the plant, these translocation velocities were estimated both in longitudinal direction, thus along the vascular bundle, and in horizontal direction, thus out of the bundle. The latter velocity is located below the contrast agent's velocity value of free diffusion. By adjusting a dynamic contrast-enhancing imaging technique (DCE-Imaging, Tof91) the acquisition duration of a T1-map was significantly reduced. By means of these maps, local concentrations of the contrast agent in plant stems and the siliques of the rapeseed plant could be determined. Numerous questions in plant science can only be answered by non-invasive techniques such as MRI. For this reason, besides the experimental results achieved in this work, further NMR methods were tested and provided for the investigation of plants. As an example, the study on the imaging of magnetic exchange processes are mentioned, which provided the groundwork for a possible transfer of CEST experiments (Chemical Exchange Saturation Transfer) to the plant. The results are presented in the bachelor thesis of A. J{\"a}ger Jae17, which was performed under my supervision, they find great interest under biologists. The development of new technologies, which extend the possibilities for the investigation of living organisms, is of great importance. For this reason, I have contributed to the development of the currently unpublished method RACETE (Refocused Acquisition of Chemical Exchange Transferred Excitations [Jak17, Reu17, Gut18a]). By rephasing the transferred magnetization the utilization of properties which have not been available in chemical "`exchange"' experiments is enabled. With this method a positive contrast is generated, thus a reference experiment is not mandatory. Furthermore, the image phase, which in classical experiments contains no information about the exchanged protons, can be used for the distinct identification of multiple substances which have been excited simultaneously. This recently at the Department of Experimental Physics V developed method can be used in particular for the identification of lipids and for the localization of sugars and amino acids, thus it can serve the enhancement and improvement of non-invasive analytical methods.},
  subject      = {Kernspintomografie},
  language  = {en}
}
@article{Zonneveld2019,
  author    = {Zonneveld, Ben J. M.},
  title     = {The DNA weights per nucleus (genome size) of more than 2350 species of the Flora of The Netherlands, of which 1370 are new to science, including the pattern of their DNA peaks},
  series = {Forum Geobotanicum},
  volume    = {8},
  journal   = {Forum Geobotanicum},
  issn      = {1867-9315},
  doi       = {10.3264/FG.2019.1022},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-189724},
  pages     = {24-78},
  year      = {2019},
  abstract  = {Besides external characteristics and reading a piece of DNA (barcode), the DNA weight per nucleus (genome size) via flow cytometry is a key value to detect species and hybrids and determine ploidy. In addition, the DNA weight appears to be related to various properties, such as the size of the cell and the nucleus, the duration of mitosis and meiosis and the generation time. Sometimes it is even possible to distinguish between groups or sections, which can lead to new classification of the genera. The variation in DNA weight is also useful to analyze biodiversity, genome evolution and relationships between related taxa. Moreover, it is important to know how large a genome is before one determines the base sequence of the DNA of a plant. Flow cytometry is also important for understanding fundamental processes in plants such as growth and development and recognizing chimeras. In the literature, DNA weight measurements are usually limited to one genus and often only locally (Siljak et al. 2010; Bai et al. 2012). In this study, however, it was decided to investigate all vascular plants from one country. This can also contribute to the protection of rare plants. This study is the first flora in the world whose weight of DNA per nucleus and peak patterns has been determined. More than 6400 plants, representing more than 2350 (sub)species (more than 90\%) have been collected, thanks to the help of almost 100 volunteers of Floristisch Onderzoek Nederland (Floron). Multiple specimens of many species have therefore been measured, preferably from different populations, in some cases more than fifty. For 1370 species, these values were not previously published. Moreover, a good number of the remaining 45\% are new for The Netherlands. In principle, each species has a fixed weight of DNA per nucleus. It has also been found that, especially between the genera, there are strong differences in the number of peaks that determine the DNA weight, from one to five peaks. This indicates that in a plant or organ there are sometimes nuclei with multiples of its standard DNA weight (multiple ploidy levels). It is impossible to show graphs of more than 2350 species. Therefore, we have chosen to show the peak pattern in a new way in a short formula. Within most genera there are clear differences in the DNA weights per nucleus between the species, in some other genera the DNA weight is hardly variable. Based on about twenty genera that were previously measured completely in most cases ('t Hart et al. 2003: Veldkamp and Zonneveld 2011; Soes et al. 2012; Dirkse et al. 2014, 2015; Verloove et al. 2017; Zonneveld [et al.] 2000-2018), it can be noted that even if all species of a genus have the same number of chromosomes, there can still be a difference of up to three times in the weight of the DNA. Therefore, a twice larger DNA weight does not have to indicate four sets of chromosomes. Finally, this research has also found clues to examine further the current taxonomy of a number of species or genera.},
  subject      = {Pflanzen},
  language  = {en}
}
@phdthesis{Kehrberger2021,
  author    = {Kehrberger, Sandra},
  title     = {Effects of climate warming on the timing of flowering and emergence in a tritrophic relationship: plants - bees - parasitoids},
  doi       = {10.25972/OPUS-21393},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-213932},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {The right timing of phenological events is crucial for species fitness. Species should be highly synchronized with mutualists, but desynchronized with antagonists. With climate warming phenological events advance in many species. However, often species do not respond uniformly to warming temperatures. Species-specific responses to climate warming can lead to asynchrony or even temporal mismatch of interacting species. A temporal mismatch between mutualists, which benefit from each other, can have negative consequences for both interaction partners. For host-parasitoid interactions temporal asynchrony can benefit the host species, if it can temporally escape its parasitoid, with negative consequences for the parasitoid species, but benefit the parasitoid species if it increases synchrony with its host, which can negatively affect the host species. Knowledge about the drivers of phenology and the species-specific responses to these drivers are important to predict future effects of climate change on trophic interactions. In this dissertation I investigated how different drivers act on early flowering phenology and how climate warming affects the tritrophic relationship of two spring bees (Osmia cornuta \& Osmia bicornis), an early spring plant (Pulsatilla vulgaris), which is one of the major food plants of the spring bees, and three main parasitoids of the spring bees (Cacoxenus indagator, Anthrax anthrax, Monodontomerus). In Chapter II I present a study in which I investigated how different drivers and their change over the season affect the reproductive success of an early spring plant. For that I recorded on eight calcareous grasslands around W{\"u}rzburg, Germany the intra-seasonal changes in pollinator availability, number of co-flowering plants and weather conditions and studied how they affect flower visitation rates, floral longevity and seed set of the early spring plant P. vulgaris. I show that bee abundances and the number of hours, which allowed pollinator foraging, were low at the beginning of the season, but increased over time. However, flower visitation rates and estimated total number of bee visits were higher on early flowers of P. vulgaris than later flowers. Flower visitation rates were also positively related to seed set. Over time and with increasing competition for pollinators by increasing numbers of co-flowering plants flower visitation rates decreased. My data shows that a major driver for early flowering dates seems to be low interspecific competition for pollinators, but not low pollinator abundances and unfavourable weather conditions. Chapter III presents a study in which I investigated the effects of temperature on solitary bee emergence and on the flowering of their food plant and of co-flowering plants in the field. Therefore I placed bee cocoons of two spring bees (O. cornuta \& O. bicornis) on eleven calcareous grasslands which differed in mean site temperature. On seven of these grasslands the early spring plant P. vulgaris occurred. I show that warmer temperatures advanced mean emergence in O. cornuta males. However, O. bicornis males and females of both species did not shift their emergence. Compared to the bees P. vulgaris advanced its flowering phenology more strongly with warmer temperatures. Co-flowering plants did not shift flowering onset. I suggest that with climate warming the first flowers of P. vulgaris face an increased risk of pollinator limitation whereas for bees a shift in floral resources may occur. In Chapter IV I present a study in which I investigated the effects of climate warming on host-parasitoid relationships. I studied how temperature and photoperiod affect emergence phenology in two spring bees (O. cornuta \& O. bicornis) and three of their main parasitoids (C. indagator, A. anthrax, Monodontomerus). In a climate chamber experiment with a crossed design I exposed cocoons within nest cavities and cocoons outside of nest cavities to two different temperature regimes (long-term mean of W{\"u}rzburg, Germany and long-term mean of W{\"u}rzburg + 4 °C) and three photoperiods (W{\"u}rzburg vs. Sn{\aa}sa, Norway vs. constant darkness) and recorded the time of bee and parasitoid emergence. I show that warmer temperatures advanced emergence in all studied species, but bees advanced less strongly than parasitoids. Consequently, the time period between female bee emergence and parasitoid emergence decreased in the warm temperature treatment compared to the cold one. Photoperiod influenced the time of emergence only in cocoons outside of nest cavities (except O. bicornis male emergence). The data also shows that the effect of photoperiod compared to the effect of temperature on emergence phenology was much weaker. I suggest that with climate warming the synchrony of emergence phenologies of bees and their parasitoids will amplify. Therefore, parasitism rates in solitary bees might increase which can negatively affect reproductive success and population size. In this dissertation I show that for early flowering spring plants low interspecific competition for pollinators with co-flowering plants is a major driver of flowering phenology, whereas other drivers, like low pollinator abundances and unfavourable weather conditions are only of minor importance. With climate warming the strength of different drivers, which act on the timing of phenological events, can change, like temperature. I show that warmer temperatures advance early spring plant flowering more strongly than bee emergence and flowering phenology of later co-flowering plants. Furthermore, I show that warmer temperatures advance parasitoid emergence more strongly than bee emergence. Whereas temperature changes can lead to non-uniform temporal shifts, I demonstrate that geographic range shifts and with that altered photoperiods will not change emergence phenology in bees and their parasitoids. In the tritrophic system I investigated in this dissertation climate warming may negatively affect the reproductive success of the early spring plant and the spring bees but not of the parasitoids, which may even benefit from warming temperatures.},
  subject      = {Biene <Gattung>},
  language  = {en}
}
@phdthesis{Kunz2023,
  author    = {Kunz, Marcel},
  title     = {Diffusion kinetics of organic compounds and water in plant cuticular model wax under the influence of diffusing barrier-modifying adjuvants},
  doi       = {10.25972/OPUS-27487},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-274874},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {To reach their target site, systemic pesticides must enter the plant from a spray droplet applied in the field. The uptake of an active ingredient (AI) takes place via the barrier-forming cuticular membrane, which is the outermost layer of the plant, separating it from the surrounding environment. Formulations are usually used which, in addition to the AI, also contain stabilizers and adjuvants. Adjuvants can either have surface-active properties or they act directly as barrier-modifying agents. The latter are grouped in the class of accelerating adjuvants, whereby individual variants may also have surface-active properties. The uptake of a pesticide from a spray droplet depends essentially on its permeability through the cuticular barrier. Permeability defines a combined parameter, which is the product of AI mobility and AI solubility within the cuticle. In recent decades, several tools have been developed that allowed the determination of individual parameters of organic compound penetration across the cuticular membrane. Nevertheless, earlier studies showed that mainly cuticular waxes are the barrier-determining component of the cuticular membrane and additionally, it was shown that mainly the very-long-chain aliphatic compounds (VLCAs) are responsible for establishing an effective barrier. However, the barrier-determining role of the individual VLCAs, being classified according to their respective functional groups, is still unknown. Therefore, the following objectives were pursued and achieved in this work: (1) A new ATR-FTIR-based approach was developed to measure the temperature-dependent real-time diffusion kinetics of organic models for active ingredients (AIs) in paraffin wax, exclusively consisting of very-long chain alkanes. (2) The developed ATR-FTIR approach was applied to determine the diffusion kinetics of self-accelerating adjuvants in cuticular model waxes of different VLCA composition. At the same time, wax-specific changes were recorded in the respective IR spectra, which provided information about the respective wax modification. (3) The ATR-FTIR method was used to characterize the diffusion kinetics, as well as to determine the wax-specific sorption capacities for an AI-modeling organic compound and water in cuticular model waxes after adjuvant treatment. Regarding the individual chemical compositions and structures, conclusions were drawn about the adjuvant-specific modes of action (MoA). In the first chapter, the ATR-FTIR based approach to determine organic compound diffusion kinetics in paraffin wax was successfully established. The diffusion kinetics of the AI modelling organic compounds heptyl parabene (HPB) and 4-cyanophenol (CNP) were recorded, comprising different lipophilicities and molecular volumes typical for AIs used in pesticide formulations. Derived diffusion coefficients ranged within 10-15 m2 s-1, thus being thoroughly higher than those obtained from previous experiments using an approach solely investigating desorption kinetics in reconstituted cuticular waxes. An ln-linear dependence between the diffusion coefficients and the applied diffusion temperature was demonstrated for the first time in cuticular model wax, from which activation energies were derived. The determined activation energies were 66.2 ± 7.4 kJ mol-1 and 56.4 ± 9.8 kJ mol-1, being in the expected range of already well-founded activation energies required for organic compound diffusion across cuticular membranes, which again confirmed the significant contribution of waxes to the cuticular barrier. Deviations from the assumed Fickian diffusion were attributed to co-occurring water diffusion and apparatus-specific properties. In the second and third chapter, mainly the diffusion kinetics of accelerating adjuvants in the cuticular model waxes candelilla wax and carnauba wax were investigated, and simultaneously recorded changes in the wax-specific portion of the IR spectrum were interpreted as indications of plasticization. For this purpose, the oil derivative methyl oleate, as well as the organophosphate ester TEHP and three non-ionic monodisperse alcohol ethoxylates (AEs) C12E2, C12E4 and C12E6 were selected. Strong dependence of diffusion on the respective principal components of the mainly aliphatic waxes was demonstrated. The diffusion kinetics of the investigated adjuvants were faster in the n-alkane dominated candelilla wax than in the alkyl ester dominated carnauba wax. Furthermore, the equilibrium absorptions, indicating equilibrium concentrations, were also higher in candelilla wax than in carnauba wax. It was concluded that alkyl ester dominated waxes feature higher resistance to diffusion of accelerating adjuvants than alkane dominated waxes with shorter average chain lengths due to their structural integrity. This was also found either concerning candelilla/policosanol (n-alcohol) or candelilla/rice bran wax (alkyl-esters) blends: with increasing alcohol concentration, the barrier function was decreased, whereas it was increased with increasing alkyl ester concentration. However, due to the high variability of the individual diffusion curves, only a trend could be assumed here, but significant differences were not shown. The variability itself was described in terms of fluctuating crystalline arrangements and partial phase separation of the respective wax mixtures, which had inevitable effects on the adjuvant diffusion. However, diffusion kinetics also strongly depended on the studied adjuvants. Significantly slower methyl oleate diffusion accompanied by a less pronounced reduction in orthorhombic crystallinity was found in carnauba wax than in candelilla wax, whereas TEHP diffusion was significantly less dependent on the respective wax structure and therefore induced considerable plasticization in both waxes. Of particular interest was the AE diffusion into both waxes. Differences in diffusion kinetics were also found here between candelilla blends and carnauba wax. However, these depended equally on the degree of ethoxylation of the respective AEs. The lipophilic C12E2 showed approximately Fickian diffusion kinetics in both waxes, accompanied by a drastic reduction in orthorhombic crystallinity, especially in candelilla wax, whereas the more hydrophilic C12E6 showed significantly retarded diffusion kinetics associated with a smaller effect on orthorhombic crystallinity. The individual diffusion kinetics of the investigated adjuvants sometimes showed drastic deviations from the Fickian diffusion model, indicating a self-accelerating effect. Hence, adjuvant diffusion kinetics were accompanied by a distinct initial lag phase, indicating a critical concentration in the wax necessary for effective penetration, leading to sigmoidal rather than to exponential diffusion kinetics. The last chapter dealt with the adjuvant-affected diffusion of the AI modelling CNP in candelilla and carnauba wax. Using ATR-FTIR, diffusion kinetics were recorded after adjuvant treatment, all of which were fully explicable based on the Fickian model, with high diffusion coefficients ranging from 10-14 to 10-13 m2 s-1. It is obvious that the diffusion coefficients presented in this work consistently demonstrated plasticization induced accelerated CNP mobilities. Furthermore, CNP equilibrium concentrations were derived, from which partition- and permeability coefficients could be determined. Significant differences between diffusion coefficients (mobility) and partition coefficients (solubility) were found on the one hand depending on the respective waxes, and on the other hand depending on treatment with respective adjuvants. Mobility was higher in candelilla wax than in carnauba wax only after methyl oleate treatment. Treatment with TEHP and AEs resulted in higher CNP mobility in the more polar alkyl ester dominated carnauba wax. The partition coefficients, on the other hand, were significantly lower after methyl oleate treatment in both candelilla and carnauba wax as followed by TEHP or AE treatment. Models were designed for the CNP penetration mode considering the respective adjuvants in both investigated waxes. Co-penetrating water, which is the main ingredient of spray formulations applied in the field, was likely the reason for the drastic differences in adjuvant efficacy. Especially the investigated AEs favored an enormous water uptake in both waxes with increasing ethoxylation level. Surprisingly, this effect was also found for the lipophilic TEHP in both waxes. This led to the assumption that the AI permeability is not exclusively determined by adjuvant induced plasticization, but also depends on a "secondary plasticization", induced by adjuvant-attracted co-penetrating water, consequently leading to swelling and drastic destabilization of the crystalline wax structure. The successful establishment of the presented ATR-FTIR method represents a milestone for the study of adjuvant and AI diffusion kinetics in cuticular waxes. In particular, the simultaneously detectable wax modification and, moreover, the determinable water uptake form a perfect basis to establish the ATR-FTIR system as a universal screening tool for wax-adjuvants-AI-water interaction in crop protection science.},
  subject      = {Pflanzen},
  language  = {en}
}
@phdthesis{Li2023,
  author    = {Li, Kunkun},
  title     = {Dissecting the interconnection of Ca\(^{2+}\) and pH signaling in plants with a novel biosensor for dual imaging},
  doi       = {10.25972/OPUS-24973},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-249736},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Calcium ion (Ca2+) and protons (H+) are both regarded as second messengers, participating in plant growth and stress mechanisms. However, H+ signals in plant physiology are less well investigated compared to Ca2+ signals. If interconnections between these two second messengers exist remains to be uncovered because appropriate imaging tools to monitor Ca2+ and H+ simultaneously in the same cell as well as accurate bioinformatics analysis remain to be developed. To overcome this problem and unravel the role and possible interconnection of Ca2+ and H+ in plants, a new biosensor named CapHensor was developed and optimized to visualize intracellular Ca2+ and H+ changes simultaneously and ratiometrically in the same cell. The CapHensor consisted of an optimized green fluorescent pH sensor (PRpHluorin) and an established red fluorescent Ca2+ sensor (R-GECO1) that were combined in one construct via a P2A sequence. A P2A self-cleavage site between the two sensors allowed to express equal amounts but spatially separated sensors, which enabled artifact-free and ratiometric imaging of cellular Ca2+ and pH side-by-side. The function of the CapHensor was verified in pollen tubes, since they possess standing Ca2+ and pH gradients. We found better imaging quality and the signal-to-noise ratio to be enhanced in live-cell imaging when two R-GECO1 proteins were fused in tandem within the CapHensor construct. To guarantee exclusive subcellular localization and avoid mixed signals from different compartments, Nuclear Export Sequence (NES) and Nuclear Localization Sequence (NLS) were used to target PRpHluorin and R-GECO1 to distinct compartments. After optimization and verification its function, CapHensor was successfully expressed in different cell types to investigate the role of Ca2+ and H+ signals to control polar growth of pollen tube, stomatal movement or leaf defense signaling. Results obtained in the past indicated both Ca2+ gradients and pH gradients in pollen tubes play roles in polar growth. However, the role and temporal relationship between the growth process and changes in Ca2+ and pH have not been conclusively resolved. Using CapHensor, I found cytosolic acidification at the tip could promote and alkalization to suppress growth velocity in N. tabacum pollen tubes, indicating that cytosolic H+ concentrations ([H+]cyt) play an important role in regulation pollen tubes growth despite the accompanied changes in cytosolic Ca2+ concentrations ([Ca2+]cyt). Moreover, growth correlated much better with the tip [H+]cyt regime than with the course of the tip [Ca2+]cyt regime. However, surprisingly, tip-focused [Ca2+]cyt andII [H+]cyt oscillations both lagged behind growth oscillations approximately 33 s and 18 s, respectively, asking for a re-evaluation of the role that tip [Ca2+]cyt may play in pollen tube growth. Live-cell CapHensor imaging combined with electrophysiology uncovered that oscillatory membrane depolarization correlated better with tip [H+]cyt oscillations than with tip [Ca2+]cyt oscillations, indicative for a prominent role of [H+]cyt to also control electrogenic membrane transport. Using CapHensor, reading out cellular movement at the same time enabled to provide a precise temporal and spatial resolution of ion signaling events, pointing out a prominent role of [H+]cyt in pollen tube tip growth. For leaf cells, a special CapHensor construct design had to be developed, containing additional NES localization sequences to avoid overlapping of fluorescense signals from the nucleus and the cytosol. Once this was achieved, the role of Ca2+ and pH changes in guard cells, another typical single-cell system was investigated. Cytosolic pH changes have been described in stomatal movement, but the physiological role of pH and the interaction with changing Ca2+ signals were still unexplored. Combining CapHensor with the here developed technique to monitor stomatal movement in parallel, the role of Ca2+ and H+ in stomatal movement was studied in detail and novel aspects were identified. The phytohormone ABA and the bacterial elicitor flagellin (flg22) are typical abiotic and biotic stresses, respectively, to trigger stomatal closure. What kind of Ca2+ and H+ signals by ABA and flg22 are set-off in guard cells and what their temporal relationship and role for stomatal movement is were unknown. Similar [Ca2+]cyt increases were observed upon ABA and flg22 triggered stomatal closure, but [H+]cyt dynamics differed fundamentally. ABA triggered pronounced cytosolic alkalization preceded the [Ca2+]cyt responses significantly by 57 s while stomata started to close ca. 205 s after phytohormone application. With flg22, stomatal closure was accompanied only with a mild cytosolic alkalization but the [Ca2+]cyt response was much more pronounced compared to the ABA effects. Where the cytosolic alkalization originates from was unclear but the vacuole was speculated to contribute in the past. In this thesis, vacuolar pH changes were visualized by the dye BCECF over time, basically displaying exactly the opposite course of the concentration shift in the vacuole than observed in the cytosol. This is indicative for the vacuolar pH dynamics to be coupled strongly to the cytosolic pH changes. In stomatal closure signalling, reactive oxygen species (ROS) were proposed to play a major role, however, only very high concentration of H2O2 (> 200 µM), which resulted in the loss of membrane integrity, induced stomatal closure. Unexpectedly, physiological concentrations of ROS led to cytosolic acidificationIII which was associated with stomatal opening, but not stomatal closure. To study the role of [H+]cyt to steer stomatal movement in detail, extracellular and intracellular pH variations were evoked in N. tabacum guard cells and their behaviour was followed. The results demonstrated cytosolic acidification stimulated stomatal opening while cytosolic alkalization triggered stomatal closure accompanied by [Ca2+]cyt elevations. This demonstrated pH regulation to be an important aspect in stomatal movement and to feed-back on the Ca2+-dynamics. It was remarkable that cytosolic alkalization but not [Ca2+]cyt increase seemed to play a crucial role in stomatal closure, because more pronounced cytosolic alkalization, evoked stronger stomatal closure despite similar [Ca2+]cyt increases. Increases in [Ca2+]cyt, which are discussed as an early stomatal closure signal in the past, could not trigger stomatal closure alone in my experiments, even when extremely strong [Ca2+]cyt signals were triggered. Regarding the interaction between the two second messengers, [Ca2+]cyt and [H+]cyt were negatively correlated most of the times, which was different from pollen tubes showing positive correlation of [Ca2+]cyt and [H+]cyt regimes. [Ca2+]cyt elevations were always associated with a cytosolic alkalization and this relationship could be blocked by the presence of vanadate, a plasma membrane H+-pump blocker, indicating plasma membrane H+-ATPases to contribute to the negative correlation of [Ca2+]cyt and [H+]cyt. To compare with guard cells, cytosolic and nuclear versions of CapHensor were expressed in N. benthamiana mesophyll cells, a multicellular system I investigated. Mesophyll cell responses to the same stimuli as tested in guard cells demonstrated that ABA and H2O2 did not induce any [Ca2+]cyt and [H+]cyt changes while flg22 induced an increase in [Ca2+]cyt and [H+]cyt, which is different from the response in guard cells. I could thus unequivocally demonstrate that guard cells and mesophyll cells do respond differently with [Ca2+]cyt and [H+]cyt changes to the same stimuli, a concept that has been proposed before, but never demonstrated in such detail for plants. Spontaneous Ca2+ oscillations have been observed for a long time in guard cells, but the function or cause is still poorly understood. Two populations of oscillatory guard cells were identified according to their [Ca2+]cyt and [H+]cyt phase relationship in my study. In approximately half of the oscillatory cells, [H+]cyt oscillations preceded [Ca2+]cyt oscillations whereas [Ca2+]cyt was the leading signal in the other half of the guard cells population. Strikingly, natural [H+]cyt oscillations were dampened by ABA but not by flg22. This effect could be well explained by dampening of vacuolar H+ oscillations in the presence of ABA, but not through flg22. Vacuolar pH contributes to spontaneous [H+]cyt oscillations and ABA but not flg22 can block the interdependence of naturalIV [Ca2+]cyt and [H+]cyt signals. To study the role of [Ca2+]cyt oscillations in stomatal movement, solutions containing high and low KCl concentrations were applied aiming to trigger [Ca2+]cyt oscillations. The triggering of [Ca2+]cyt oscillations by this method was established two decades ago leading to the dogma that [Ca2+]cyt increases are the crucial signal for stomatal closure. However, I found stomatal movement by this method was mainly due to osmotic effects rather than [Ca2+]cyt increases. Fortunately, through this methodology, I found a strong correlation between cytosolic pH and the transport of potassium across the plasma membrane and vacuole existed. The plasma membrane H+-ATPases and H+-coupled K+ transporters were identified as the cause of [H+]cyt changes, both very important aspects in stomata physiology that were not visualized experimentally before. Na+ transport is also important for stomatal regulation and leaves generally since salt can be transported from the root to the shoot. Unlike well-described Ca2+- dependent mechanisms in roots, how leaves process salt stress is not at all understood. I applied salt on protoplasts from leaves, mesophyll cells and guard cells and combined live-cell imaging with Vm recordings to understand the transport and signaling for leaf cells to cope with salt stress. In both, mesophyll and guard cells, NaCl did not trigger Ca2+-signals as described for roots but rather triggered Ca2+ peaks when washing salt out. However, membrane depolarization and pronounced alkalinization were very reliably triggered by NaCl, which could presumably act as a signal for detoxification of high salt concentrations. In line with this, I found the vacuolar cation/H+ antiporter NHX1 to play a role in sodium transport, [H+]cyt homeostasis and the control of membrane potential. Overexpression of AtNHX1 enabled to diminish [H+]cyt changes and resulted in a smaller depolarization responses druing NaCl stress. My results thus demonstrated in contrast to roots, leaf cells do not use Ca2+-dependent signalling cascades to deal with salt stress. I could show Na+ and K+ induced [H+]cyt and Vm responses and Cl- transport to only have a minor impact. Summing all my results up briefly, I uncovered pH signals to play important roles to control pollen tube growth, stomatal movement and leaf detoxification upon salt. My results strongly suggested pH changes might be a more important signal than previously thought to steer diverse processes in plants. Using CapHensor in combination with electrophysiology and bioinformatics tools, I discovered distinct interconnections between [Ca2+]cyt and [H+]cyt in different cell types and distinct [Ca2+]cyt and [H+]cyt signals are initiated through diverse stimuli and environmental cues. The CapHensor will be very useful in the future to further investigate the coordinated role of Ca2+ and pH changes in controlling plant physiology.},
  subject      = {Pflanzen},
  language  = {en}
}
@article{KirchmeierMeierottJung2023,
  author    = {Kirchmeier, Peter and Meierott, Lenz and Jung, Klaus},
  title     = {Taraxacum sect. Borealia Hand.-Mazz. in den Alpen},
  series = {Forum Geobotanicum},
  volume    = {11},
  journal   = {Forum Geobotanicum},
  issn      = {1867-9315},
  doi       = {10.3264/FG.2023.1230},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-347512},
  pages     = {35-56},
  year      = {2023},
  abstract  = {The presence of Taraxacum microspecies of the section Borealia in the European Alps has been known from France, Suisse, Austria, Italy and Slowenia. The five known species are Taraxacum gallicum, T. handelii, T. kraettlii, T. mazzettii and T. melzerianum. From 2004 up to 2014 these localities have been visited. Detailed examinations of many collections make it possible to add characteristics and precise the descriptions and correct mistakes, eliminate ambiguities and fill gaps in the original descriptions. Numerous photos, drawings and a new determination key will make the access to the section Borealia easier. A new species of section Borealia, T. cimae-gallinae, from the mountain H{\"u}hnerspiel near Sterzing (Italy, South Tyrol) is described. The habitats of the Borealia in the alpine level are mostly gravel floors on wind-swept ridges or on summit levelings. The environment of Borealia-species is threatened by ski tourism or by the changes from global warming.},
  subject      = {Pflanzen},
  language  = {de}
}
@phdthesis{Masota2023,
  author    = {Masota, Nelson Enos},
  title     = {The Search for Novel Effective Agents Against Multidrug-Resistant Enterobacteriaceae},
  doi       = {10.25972/OPUS-30263},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-302632},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {This thesis aimed at searching for new effective agents against Multidrug-Resistant Enterobacteriaceae. This is necessitated by the urgent need for new and innovative antibacterial agents addressing the critical priority pathogens prescribed by the World Health Organization (WHO). Among the available means for antibiotics discovery and development, nature has long remained a proven, innovative, and highly reliable gateway to successful antibacterial agents. Nevertheless, numerous challenges surrounding this valuable source of antibiotics among other drugs are limiting the complete realization of its potential. These include the availability of good quality data on the highly potential natural sources, limitations in methods to prepare and screen crude extracts, bottlenecks in reproducing biological potentials observed in natural sources, as well as hurdles in isolation, purification, and characterization of natural compounds with diverse structural complexities. Through an extensive review of the literature, it was possible to prepare libraries of plant species and phytochemicals with reported high potentials against Escherichia coli and Klebsiella pneumnoniae. The libraries were profiled to highlight the existing patterns and relationships between the reported antibacterial activities and studied plants' families and parts, the type of the extracting solvent, as well as phytochemicals' classes, drug-likeness and selected parameters for enhanced accumulation within the Gram-negative bacteria. In addition, motivations, objectives, the role of traditional practices and other crucial experimental aspects in the screening of plant extracts for antibacterial activities were identified and discussed. Based on the implemented strict inclusion criteria, the created libraries grant speedy access to well-evaluated plant species and phytochemicals with potential antibacterial activities. This way, further studies in yet unexplored directions can be pursued from the indicated or related species and compounds. Moreover, the availability of compound libraries focusing on related bacterial species serves a great role in the ongoing efforts to develop the rules of antibiotics penetrability and accumulation, particularly among Gram-negative bacteria. Here, in addition to hunting for potential scaffolds from such libraries, detailed evaluations of large pool compounds with related antibacterial potential can grant a better understanding of structural features crucial for their penetration and accumulation. Based on the scarcity of compounds with broad structural diversity and activity against Gram-negative bacteria, the creation and updating of such libraries remain a laborious but important undertaking. A Pressurized Microwave Assisted Extraction (PMAE) method over a short duration and low-temperature conditions was developed and compared to the conventional cold maceration over a prolonged duration. This method aimed at addressing the key challenges associated with conventional extraction methods which require long extraction durations, and use more energy and solvents, in addition to larger quantities of plant materials. Furthermore, the method was intended to replace the common use of high temperatures in most of the current MAE applications. Interestingly, the yields of 16 of 18 plant samples under PMAE over 30 minutes were found to be within 91-139\% of those obtained from the 24h extraction by maceration. Additionally, different levels of selectivity were observed upon an analytical comparison of the extracts obtained from the two methods. Although each method indicated selective extraction of higher quantities or additional types of certain phytochemicals, a slightly larger number of additional compounds were observed under maceration. The use of this method allows efficient extraction of a large number of samples while sparing heat-sensitive compounds and minimizing chances for cross-reactions between phytochemicals. Moreover, findings from another investigation highlighted the low likelihood of reproducing antibacterial activities previously reported among various plant species, identified the key drivers of poor reproducibility, and proposed possible measures to mitigate the challenge. The majority of extracts showed no activities up to the highest tested concentration of 1024 µg/mL. In the case of identical plant species, some activities were observed only in 15\% of the extracts, in which the Minimum Inhibitory Concentrations (MICs) were 4 - 16-fold higher than those in previous reports. Evaluation of related plant species indicated better outcomes, whereby about 18\% of the extracts showed activities in a range of 128-512 μg/mL, some of the activities being superior to those previously reported in related species. Furthermore, solubilizing plant crude extracts during the preparation of test solutions for Antibacterial Susceptibility Testing (AST) assays was outlined as a key challenge. In trying to address this challenge, some studies have used bacteria-toxic solvents or generally unacceptable concentrations of common solubilizing agents. Both approaches are liable to give false positive results. In line with this challenge, this study has underscored the suitability of acetone in the solubilization of crude plant extracts. Using acetone, better solubility profiles of crude plant extracts were observed compared to dimethyl sulfoxide (DMSO) at up to 10 \%v/v. Based on lacking toxicity against many bacteria species at up to 25 \%v/v, its use in the solubilization of poorly water-soluble extracts, particularly those from less polar solvents is advocated. In a subsequent study, four galloylglucoses were isolated from the leaves of Paeonia officinalis L., whereby the isolation of three of them from this source was reported for the first time. The isolation and characterization of these compounds were driven by the crucial need to continually fill the pre-clinical antibiotics pipeline using all available means. Application of the bioautography-guided isolation and a matrix of extractive, chromatographic, spectroscopic, and spectrometric techniques enabled the isolation of the compounds at high purity levels and the ascertainment of their chemical structures. Further, the compounds exhibited the Minimum Inhibitory Concentrations (MIC) in a range of 2-256 µg/mL against Multidrug-Resistant (MDR) strains of E. coli and K. pneumonia exhibiting diverse MDR phenotypes. In that, the antibacterial activities of three of the isolated compounds were reported for the first time. The observed in vitro activities of the compounds resonated with their in vivo potentials as determined using the Galleria mellonella larvae model. Additionally, the susceptibility of the MDR bacteria to the galloylglucoses was noted to vary depending on the nature of the resistance enzymes expressed by the MDR bacteria. In that, the bacteria expressing enzymes with higher content of aromatic amino acids and zero or positive net charges were generally more susceptible. Following these findings, a plausible hypothesis for the observed patterns was put forward. The generally challenging pharmacokinetic properties of galloylglucoses limit their further development into therapeutic agents. However, the compounds can replace or reduce the use of antibiotics in livestock keeping as well as in the treatment of septic wounds and topical or oral cavity infections, among other potential uses. Using nature-inspired approaches, a series of glucovanillin derivatives were prepared following feasible synthetic pathways which in most cases ensured good yields and high purity levels. Some of the prepared compounds showed MIC values in a range of 128 - 512 μg/mL against susceptible and MDR strains of Klebsiella pneumoniae, Methicillin-Resistant Staphylococcus aureus (MRSA) and Vancomycin-Resistant Enterococcus faecium (VRE). These findings emphasize the previously reported essence of small molecular size, the presence of protonatable amino groups and halogen atoms, as well as an amphiphilic character, as crucial features for potential antibacterial agents. Due to the experienced limited success in the search for new antibacterial agents using purely synthetic means, pursuing semi-synthetic approaches as employed in this study are highly encouraged. This way, it is possible to explore broader chemical spaces around natural scaffolds while addressing their inherent limitations such as solubility, toxicity, and poor pharmacokinetic profiles.},
  subject      = {Enterobacteriaceae},
  language  = {en}
}